Iceland's managing director, Richard Walker, has penned an open letter to customers thanking them for their part in stopping palm oil-induced deforestation following a furore over the supermarket's 'banned' Christmas ad.

The boss said the controversy around the ad being prevented from broadcast on legal grounds has "re-written" all of the traditional rules.

The spot was designed to underline Iceland's commitment to removing palm oil from its own-brand products, which was announced in April. However due to rules around political advertising the association with Greenpeace meant Iceland's Christmas campaign was never approved for broadcast by ad vetting body Clearcast. While it didn't show on TV, it garnered sweeping momentum across Facebook, Twitter and YouTube thanks in part to support from celebrities like James Corden.

In an open letter, published in the Guardian on Saturday (1 December) Walker said that when the ad failed to meet Clearcast standards he was "genuinely mortified".

"While we understand and respect the Clearcast decision, I feared that we would be without the showcase ad that was designed to raise awareness of an important issue," he explained. "But the 'ban' has re-written all of the traditional rules."

According to Walker, the ad has clocked up 70 million views and counting online.

"Far from being a cynical PR ploy all along, this was a genuine case of serendipity. I think it proved just how engaged and concerned consumers are with this issue, and it raised a global debate around the pros and cons of palm oil and deforestation," he added.

Walked pointed out that a petition to get Clearcast's legal decision overturned, started by a customer in November, hit 1 million signature this week. He also noted that on 15 November the Roundtable on Sustainable Paml Oil (RSPO) – the industry body that works towards sustainable palm oil production – incorporated 'no deforestation' into its new principles.

"I would like to take this opportunity to thank all of you who have supported [Iceland's] campaign," wrote Walker.

"I believe that the consumer pressure which has gathered pace since our announcement in April has helped, alongside many other other calls to action.

"The last few weeks have shown how much people actually care. It shows the real power of individual and the ability for us to effect meaningful change," he finished.

Clearcast was forced to temporarily shut down its Facebook page and switchboard following abuse directed at its staff in the wake of the Iceland controversy,

He cited Greenpeace's involvement as the barrier to broadcast for Iceland, rather than the content of the ad itself.

The stumbling point, said Mundy, was that the film was originally created by Greenpeace. Iceland's TV offering was spiked because it was deemed to be "an advertisement inserted by or on behalf of a body whose objects are wholly or mainly of a political nature".

Mundy explained that for Iceland to overcome the ruling, "Greenpeace needs to demonstrate it is not a political advertiser."

You can watch the Iceland ad below. The original Greenpeace animation was created by Mother London.